In order to enable wireless communication between a train which travels on a railroad track and a ground facility (for example, an operation command room), a train radio system which is one kind of a mobile communication system is provided. The railroad track can be regarded as one line (in a case in which it is required to distinguish two lines in both directions in a double track section, two closed lines) when it is seen in broad perspective. Accordingly, a service area of the train radio system is an area along such line. Therefore, in a common train radio system, a long antenna such as a leaky coaxial cable (LCX) or the like is installed near the railroad track and along the railroad track and a base station is connected to this antenna. On the other hand, in a common train radio system, the in-vehicle device is installed in a train. In the train radio system using the LCX, a radio wave leaked from the LCX installed along the railroad track is received by a train side device (in-vehicle device) and whereby, communicate between the ground facility and a train can be performed. The LCX is also used as countermeasures against a dead zone such as a tunnel in which mobile telephone service cannot be offered because a radio wave does not reach. Further, when a layout of the railroad track is determined from a geographical viewpoint, the service area of the train radio system may be spread in a planar shape.
A mobile communication system similar to the train radio system used for a railroad or a track can also be applied to for example, bus transit (as an example, a BRT (Bus Rapid Transit) system) or the like that uses an exclusive road or an open road. Accordingly, in this description, the railroad track of the railroad or the track, a ropeway, a guide rail, a road, and the like are called as a route. In this kind of the mobile communication system, when the length of the route is long, base stations are deployed at an interval of several kilometers along the route, the LCX is connected to all the base stations, and a plurality of base stations are connected to a central control device by a wire cable. The mobile communication system is configured in such a way that the central control device controls a plurality of the base stations. In a case in which the interval between the base stations is greater than the length of one LCX, a plurality of the LCXs are laid along the route and each LCX is connected to the base station by a relay cable.
In order to stably operate the mobile communication system represented by the train radio system, it is required to quickly detect the occurrence of failure or fault in the LCX and the base station connected to the LCX and identify the fault location. However, in order to detect a failure or a fault in these devices and identify a fault location, in general, it is required to perform an on-site investigation and it takes a huge cost and a very long time. In PTL (patent literature) 1, it is disclosed a method for detecting a position of a crack, a fracture, or the like in an early stage of the LCX with a high degree of accuracy in which a detection sensor composed of a loop antenna is moved along the LCX and the fault location is detected based on the leaked electromagnetic field strength.
As a method for detecting a position of each train on a route, for example, in patent literature 2, it is disclosed a method in which the position of the train is detected by a train side device by using the GPS (Global Positioning System) and a modulation scheme of the train radio system is changed according to the detected position.